1. Field of the Invention
The present invention relates to a method and a device for carrying out measurements and/or operations in a well at the level of the surrounding formations, and more particularly formations subjected to hydraulic compression. The invention is more especially applicable when it is a question of carrying out measurements and/or operations at the level of geological formations situated in a zone which must be isolated from the rest of the well and into which a pressurized hydraulic fluid is injected so as to fracture the formations at this level (hydraulic fracturing process).
2. Description of the Prior Art
Prior hydraulic fracturing techniques are described for example in U.S. Pat. No. 3,427,652.
The measurements carried out by application of the present invention may for example comprise the triaxial recording of the noises produced by the rocks thus placed under stress. From the analysis of the vibrations detected, the orientation of the noise source can be defined and consequently the direction of propagation of the fracture. This analysis technique is well known by geophysiciens and will not be described here in greater detail.
Techniques of the prior art for determining the propagation of fractures in the ground are described for example in U.S. Pat. Nos. 3,739,871 and 3,775,739.
The measurements made may also comprise the recording of the pressure and of the bore-bottom temperature, the measurements (focused or not) of the electric resistivity of the formations, etc.
These measurements may be completed by displaying the walls of the well by means of a television camera for example.
One of the objects of the invention is to provide a device more especially for moving a measurement or operation instrument in a well zone possibly subjected to hydraulic compression, not only during but also at the end of the hydraulic fracturing of the formations surrounding this zone.
A device is already known from U.S. Pat. No. 4,349,072 for carrying out measurements and/or operations in a well, this device comprising tubing open at its lower end and having a diameter less than that of the well, a measuring or operation instrument (probe) moveable by remote control from the surface between a first position in which the instrument is housed in the lower part of the tubing forming a protecting casing and a second position in which said instrument leaves said tubing at least partially at the lower end thereof, to allow the measurement or operation and an electric transmission cable equipped with a first electric connection member adapted to be placed in the tubing so as to engage with a second electric connection member connected to said instrument.
A technique is also known from U.S. Pat. No. 2,153,254 for carrying out fluid production tests from geological formations through which a well passes, by using tubing provided at its lower part with a sealing member, or packer, coming to bear against a zone of the walls of the well having a conical shape.
These production tests comprise the monitoring and recording at the surface of the noises created by the flow of fluids produced by the geological formations.